 /*******************************************************************************
  * Copyright (c) 2007 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui.internal;

 import java.util.Arrays ;
 import java.util.Collections ;
 import java.util.Iterator ;
 import java.util.List ;

 import org.eclipse.core.expressions.ICountable;
 import org.eclipse.core.expressions.IIterable;
 import org.eclipse.core.runtime.IAdapterFactory;
 import org.eclipse.jface.viewers.ISelection;
 import org.eclipse.jface.viewers.IStructuredSelection;

 /**
  * Adapts ISelection instances to either IIterable or ICountable. For use with
  * core expressions.
  *
  * @since 3.3
  */
 public class SelectionAdapterFactory implements IAdapterFactory {
     private static final ICountable ICOUNT_0 = new ICountable() {
         /*
          * (non-Javadoc)
          *
          * @see org.eclipse.core.expressions.ICountable#count()
          */
         public int count() {
             return 0;
         }
     };
     private static final ICountable ICOUNT_1 = new ICountable() {
         /*
          * (non-Javadoc)
          *
          * @see org.eclipse.core.expressions.ICountable#count()
          */
         public int count() {
             return 1;
         }
     };
     private static final IIterable ITERATE_EMPTY = new IIterable() {
         /*
          * (non-Javadoc)
          *
          * @see org.eclipse.core.expressions.IIterable#iterator()
          */
         public Iterator iterator() {
             return Collections.EMPTY_LIST.iterator();
         }
     };

     /**
      * The classes we can adapt to.
      */
     private static final Class [] CLASSES = new Class [] { IIterable.class,
             ICountable.class };

     public Object getAdapter(Object adaptableObject, Class adapterType) {
         if (adaptableObject instanceof ISelection) {
             if (adapterType == IIterable.class) {
                 return iterable((ISelection) adaptableObject);
             } else if (adapterType == ICountable.class) {
                 return countable((ISelection) adaptableObject);
             }
         }
         return null;
     }

     private Object iterable(final ISelection sel) {
         if (sel.isEmpty()) {
             return ITERATE_EMPTY;
         }
         if (sel instanceof IStructuredSelection) {
             return new IIterable() {
                 public Iterator iterator() {
                     return ((IStructuredSelection) sel).iterator();
                 }
             };
         }
         final List list = Arrays.asList(new Object [] { sel });
         return new IIterable() {

             public Iterator iterator() {
                 return list.iterator();
             }
         };
     }

     private Object countable(final ISelection sel) {
         if (sel.isEmpty()) {
             return ICOUNT_0;
         }
         if (sel instanceof IStructuredSelection) {
             final IStructuredSelection ss = (IStructuredSelection) sel;
             return new ICountable() {
                 public int count() {
                     return ss.size();
                 }
             };
         }
         return ICOUNT_1;
     }

     public Class [] getAdapterList() {
         return CLASSES;
     }
 }

